1. Field of the Invention
The invention relates to a vehicle propulsion system with selectable energy sources and its method of use.
2. Background Art
Today it is becoming increasingly desirable to reduce the use of gasoline to fuel transportation. A number of alternative fuel sources have begun to emerge. However, the variations of applications to which vehicles are generally put are typically satisfied only by inclusion of a gasoline powered internal combustion engine. A significant consideration is the ability to travel up to several hundred miles in one day. However, for most applications, a vehicle travels no more than about thirty miles a day.
As a consequence, hybrid and conventional vehicles capable of using an alternate energy source for propulsion technologies often combine propulsion technologies with gasoline powered engines for the few occasions when long distance travel is needed. Alternate propulsion technologies include electric motors and internal combustion engines fueled by different sources of energy. The different sources of energy are often constrained by the ability to store energy on the vehicle. One example of such a constraint is an energy battery that can act as a source of energy for an electric motor in the vehicle. For the energy battery to provide sufficient energy to power the vehicle for thirty miles every day, it must be relatively large. The problem is that the incremental cost of the large energy battery makes it a limited option for the average consumer. Many energy batteries used in vehicles today provide only about six miles of daily travel, according to the Environmental Protection Agency cycle driving method.
While many energy batteries used in vehicles today recharge from regenerative braking, it is desirable to have a method of completely recharging, such as plug-in recharging capabilities that use a standard household electric service provided from a commercial electrical grid.
An alternative source of energy that can be stored on a vehicle is hydrogen. Gaseous hydrogen is currently used in vehicles having a fuel cell or hydrogen-fueled internal combustion engine. U.S. Pat. No. 5,785,136 describes a hybrid drive arrangement having a thermal engine that can be operated on a fuel containing hydrocarbons, and is capable of generating hydrogen. The hydrogen is stored in a device on the vehicle. The source of hydrogen fuel for this vehicle is methanol passed through a reformer located on the vehicle. Reformer technology, and in particular the membranes on reformers, is an expensive option and subject to high maintenance needs. In addition, using methanol as an onboard fuel source would require fuel stations to have sources of methanol in addition to gasoline. This is not very economical for the service station providers.
What is needed is a hybrid vehicle propulsion system that is relatively inexpensive, relatively easy to use, and has controls, fuels, and propulsion components that cooperate to reduce the use of gasoline to fuel transportation, while having a gasoline-powered propulsion system available for certain transportation needs.